Humans may be the only species known to be able to throw trash into space. This sentence is not "Versailles", and even a hint of helplessness.
We are still far from being able to send household garbage to space at low cost. The garbage mentioned in the above sentence refers to "abandoned or damaged satellites and debris." There are more and more of them, quietly revolving around the earth. , Becomes a veritable "net".
If human beings look to the more distant space age, it can be said that the problem of space junk and domestic junk is equally serious. The only difference is whether the junk surrounds the city or the earth.
Musk’s Starlink satellites, scientists say about 3% have failed
SpaceX’s Starlink project has attracted a lot of attention since its inception, and its popularity has not diminished, not only because of the “bold” nature of the plan, but also because it expects the total number of satellites to be launched to reach an astonishing number: 42,000. .
The reason for launching so many satellites is that Starlink plans to build a satellite network covering the world to provide broadband services to users on the earth, and to a certain extent solve the network problems in remote areas and special areas of the natural environment-in sparsely populated areas Or where people are inaccessible, it is not very economical to establish base stations that require human maintenance from time to time.
According to the European Space Agency's Space Debris Office (SDO), as of February 2020, there are approximately 5,500 satellites in orbit.
In other words, the total number of satellites launched by only one Starlink plan is more than 7 times the total number of satellites in orbit before .
No matter how scientific and technological the word satellite sounds, it is still a large "electronic product" in the final analysis, and it has to go through many tests such as lift-off and orbit change, and malfunctions are inevitable.
▲ Picture from: NASA (Unsplash)
Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, compared data from SpaceX and the US government, and speculated that about 3% of the more than 800 Starlink satellites that have been launched into the sky may have failed . The satellite "may have disintegrated or crashed into the atmosphere to burn."
Why is the low failure rate of 3% cause for concern?
Astronomer Jonathan McDowell said that a failure rate of 3% is a normal level, while SpaceX believes that the failure rate is only about 1%. In other words, SpaceX also recognizes the existence of the failure and acknowledges the fact that the failure has occurred.
If calculated at a failure rate of 3%, about 1260 satellites will fail out of 42,000 satellites. If calculated at a failure rate of 1%, this number is 420.
▲ The movie "Robots" shows the earth wrapped in a failed satellite
According to data from the European Space Agency’s Space Debris Office (SDO), by February 2020, there will be about 3,200 failed satellites. After that, the failure of only one project of the Starlink project may have reached the failure of humans for decades. 12%-38% of the total number of satellites.
At present, all countries in the world are preparing to build a space Internet, and the number of satellites to be launched is increasing geometrically. Some scientists predict that the total number of satellites planned to be launched in the future may exceed 100,000. Regardless of whether the failure rate is 3% or 1%, the number of failed satellites is a huge number.
Leaving the total to talk about the incidence, it is all…
Space is so big that it can’t accommodate dead satellites?
Many people think that satellites are small and space is very large. Satellites are not even a piece of sand in space. If they fail, they will fail.
But in fact, failed satellites are like time bombs, which can cause devastating damage to other satellites at any time.
▲ The high-speed debris in space is extremely lethal. Image source: "Interstellar" movie
There are several keywords involved: orbit, collision, and debris. When these three factors come together, a failed satellite is a big problem.
1. Satellite orbit and frequency resources are becoming scarcer
Geosynchronous orbital locations are very scarce. Coupled with the need to keep space between satellites to avoid radio interference, "the space is so large that you can squeeze satellites at will."
In order to alleviate the shortage of orbital resources, the ITU will allocate satellite orbital positions based on multiple factors such as the territorial area and population of each country. Just like the current license plates in first-tier cities, there are only so many roads. Human competition will become more intense.
Ineffective satellites also occupy orbits, wasting valuable resources. According to the Beijing Daily, the reason why China's Beidou satellite "launched in the last four hours" is also due to orbital and frequency resource factors.
▲ Schematic diagram of Beidou satellite. Picture from: Beidou Navigation System official website
This is because on April 18, 2000, the ITU approved the frequency and orbit of the navigation satellites declared by China. The "Beidou" satellite navigation system entered the ITU frequency list and formally obtained legal status. However, according to international rules, if it is not used within 7 years of registration, that is, before April 17, 2007, the frequency will expire.
2. Failed satellites are more likely to cause collisions
Satellites that are successfully launched and are in normal service are controlled by signals and can change orbit, evade, and adjust angles. Invalid satellites are no longer controlled by humans. They are basically "floating in space" due to earth perturbation (a cause). Deviated from the orbit due to the attraction of other celestial bodies or the influence of other factors.
Many failed satellites are abandoned, and no one cares about them anymore, and they don’t know where they go around the earth. This greatly increases the risk of collisions between newly launched satellites and failed satellites.
For example, in December 2009, the third stage of the Long March 4 rocket launched by China and the abandoned satellite launched by the former Soviet Union in February 1989 almost collided at a high speed at 991 kilometers above Antarctica. When the two were closest, the distance might be only 12 Meter.
▲ Pass by
3. The debris after the collision repeatedly causes the above two problems
After a collision, the failed satellite will produce a large amount of debris. Most of the debris will be scattered in the orbit of the failed satellite and continue to revolve around the earth. This will occupy orbital resources and increase the probability of collision. A small part of the debris will be scattered. Go out and float in space. Scientists have speculated that there may be hundreds of millions of debris above the millimeter level.
▲ Debris speculation map produced by European Space Agency
How powerful are these debris?
In low-Earth orbit at a height of 300-450 kilometers, the speed of space debris may reach 7-8 kilometers per second. When they are in a geostationary orbit at an altitude of 36,000 kilometers, their speed is as high as 3 kilometers per second.
If two objects with a speed of 7 kilometers per second collide in space, debris of about 10 cm may damage the entire spacecraft or satellite, and debris of about 1 cm may penetrate the space capsule, even if it is inconspicuous on Earth Debris of about 1 mm may cause injury.
A piece of space junk weighing 10 grams hits a satellite, which is equivalent to two 100 km/h cars colliding with each other. The satellite may be penetrated or directly destroyed within 1.5 seconds, and it will directly threaten the safety of astronauts.
The International Space Station is the "living target" of satellite debris. In April 2016, a 7 mm diameter crack appeared on the ground observation deck glass on the International Space Station, which was caused by a small debris hit.
▲ Imagine the consequences of instantaneous breaking of glass
Solve invalid satellites, most of them rely on the sky
How to solve the potential hazards of failed satellites?
The answer is: mostly depends on the sky.
1. Abandonment Law
The recovery risk is high and the cost is high. The ultimate fate of a failed satellite is to continue to revolve around the earth alone. The only thing people can do is to wait for the satellite to gradually decompose on its own, or slowly fall into the atmosphere and burn out. The cycle is generally long, which may take decades.
2. "Cremation" method
At the beginning of the design of the satellite, some satellites reserved a portion of electricity and fuel, waiting for the satellite to be on the verge of failure, ignite the remaining fuel, and push the satellite into the atmosphere for combustion.
▲ According to the official website of Starlink Project, when the satellite's life ends, it will use the airborne propulsion system to de-orbit
However, the satellite is a precision-designed instrument, and the internal space is large and small. The seemingly simple "leave the back door" operation may cause problems such as increased costs or increased risks. Therefore, many satellites do not have this design.
3. Space burial
Some satellites are medium-to-high orbit satellites, which are too far away from the earth’s atmosphere, and are eventually pushed into space instead of the atmosphere.
However, since the fuel reserved for general satellites is very small, it is not enough to allow a failed satellite to fly into the depths of space. It will only fly to an unimportant or unused space orbit and still surround the earth.
4. Active cleaning
On June 25, 2016, China’s "Long March VII" was successfully launched. A space debris cleaning vehicle named "Aolong One" entered space together. It was known as a "space scavenger" and could be grabbed by a robotic arm. Satellites and space debris were brought into the atmosphere and burned.
In addition to grabbing with a mechanical arm, there are methods such as jet nets to capture failed satellites, and laser shooting of failed satellites. It can be said that "conservative therapy" still accounts for the majority, and there are more and more active treatment methods.
go ahead! go ahead! go ahead!
The Russian scientist Tsiolkovsky said: "The earth is the cradle of mankind, but mankind cannot live in the cradle forever."
With the advancement of society, when human beings enjoy the protection of the cradle of the earth, they are also facing a shortage of some resources. The improvement of productivity and production level is always limited by the objective process of the development of human civilization. Economic crisis and even war.
If we can further explore and develop space resources, we can alleviate or solve this "earth disease" to a certain extent. Launching satellites is the first step for mankind to truly enter space. After countless epochs, it will be recorded in history by new humans.
It's just that when mankind really intends to immigrate to another planet in space, if those thousands of invalid satellites floating above the earth become the biggest stumbling block for mankind to fight in space, it would be too black humor.
Whether it is exploring space or cleaning up space junk, we have only one choice: forward, forward, forward!
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